---
category: Validator
created: '2020-04-19'
title: Check if a string is lower case
updated: '2021-10-13'
---

**JavaScript version**

```js isLowerCase.js
const isLowerCase = (str) => str === str.toLowerCase();
```

**TypeScript version**

```ts isLowerCase.ts
const isLowerCase = (str: string): boolean => str === str.toLowerCase();
```
